The present invention relates to the field of manway covers and emergency pressure relief apparatus for tanks. Industrial tanks often store volatile fluids or gasses and therefore must be substantially vapor tight. Manways are provided for entry of personnel into the tank for cleaning and inspection. The manway is covered during normal operation with a manway cover to prevent the stored contents from escaping. Known manway covers are secured to the tank with nuts and bolts.
Tanks also often include pressure relief apparatus for relieving pressure in the tank. Pressure buildup can result from overpressure delivered by charging devices, such as pumps or compressors, or may result from increased temperature during an emergency event, such as a fire. It is necessary to limit the amount of pressurization within a tank; an excessively high pressure could result in the tank exploding with disastrous consequences. Conventional pressure relief valves are mounted to a pressure relief vent pipe extending from the tank interior to prevent excessive pressure build-up.